Much needed opinions here please. what is wrong here?

If a guy ignores you, avoids eye contact and pretends your not in the room, stares at you blankly in a room full of people, ignores your contribution to a conversation and your standing right there but then helps you, cracks jokes nervously, tries not to smile/ laugh when you speak to him, helps you out and chats with you happily and when you leave is grinning from ear to ear, what does this mean? I really like this person and I know he can be shy (we are both adults) but I'm sooo confused:( Sometimes his emails are friendly and other times they are blunt and cold. I replied to a friendly email in the same manner once and he went 'cold' on me again.. He once walked past me and when I looked up at him, I noticed his face was facing me but his eyes were pinned to the ground. He then turned his head away in the opposite direction and kept walking without a little acknowledgment... I am so upset about this because I really like him and can't understand what I am doing wrong